There is an example that puts you in 3/0 in the handbook but it is talking about >30c.
I have to admit I have never been in this article and it is pretty confusing the way they word it. I am not 100% sure why you wouldn't have to just use 310.16.
It does sound like they are talking about a line cord for a listed piece of equipment and just giving the NRTL some wiggle room
400.5
...These tables shall be used in conjunction with applicable end-use product standards to ensure selection of the proper size and type...
